Main Question or Discussion Point
Can someone explain to me why different terms arising from a particular electron configuration have different energies? For example, for carbon in the configuration [tex]1s^22s^22p^2[/tex] three terms arise, 3P 1D and 1S. These three terms have different energies but I don't understand why. The electron configuration is given, so what changes between the three terms? How can they have different energies?